According to the prior art, thermoformed packaging articles, such as cups and bowls, in particular for packaging foodstuffs, are sealed by a sealing film and possibly packaged using a cardboard sleeve or a covering box or additionally provided with a slid lid. Closure by means of a sealing film is necessary in order to achieve a sealing to the environment. By use of a covering package or a slid lid alone, a packaging article cannot be tightly closed according to the prior art. The fit of a lid on the container is dependent, inter alia, on the outer edge dimensions of the container, the fit size of the lid, and the configuration, position and number of nubs retaining the lid on the container. All in all, the lid fit is subject to variations which are possibly interfered with by contractions and deformations due to a sterilization process during or after filling the packaging article with foodstuffs. Such contractions or deformations cannot be taken into account and influenced by the manufacturer of the package.
The compelling use of a sealing for tightly closing the packaging article involves disadvantages, for example, in form of increased expenditure in manufacturing and materials. A further disadvantage is that a once opened packaging article cannot be tightly re-closed, thereby limiting potential uses and fill sizes of the packaging article.